Surprise! Snakes Have Clitorises

A new discovery could rewrite the story of reptilian sex.

the head of a snake with gold, brown, and black scales on red sand
Getty / Ted Mead

In her two decades as a genital morphologist, Patricia Brennan has looked at a lot of animal clitorises. She’s seen female lizards’ two spike-studded protrusions, which are almost identical to their counterparts on males. She’s glimpsed the prominent appendage through which female spotted hyenas urinate and give birth. She’s even studied the thin-skinned, nerve-laced organ of a female dolphin, which Brennan’s work suggests makes sex pleasurable. But until quite recently, she had never found a clitoris on a snake.

Brennan, to be clear, had checked. A researcher at Mount Holyoke College, she had dissected all sorts of snakes and lizards over the years and always found the same thing: Males sport a pair of heavily ornamented penises, called hemipenes, that can, like the lining of a pocket, be popped out of the base of the tail; the same trick works on many lizard females, whose clitorises, or hemiclitores, can also be flipped out. But whenever Brennan tried the maneuver on a lady snake, she turned up zip, nada, zilch. Eventually, Brennan, like many others in her field, concluded that snake clitorises must not exist.

So when her collaborator Megan Folwell, of the University of Adelaide, reached out last year to share images from a recent dissection of a female death-adder tail, “I almost fell off my chair,” Brennan told me. What Folwell had found was unmistakable: There, right below the venomous snake’s cloaca (an all-purpose, vagina-like orifice), nestled between a pair of scent glands, were two small, pink protrusions—a pair of clitorises that had never been fully documented before. Folwell, Brennan, and their colleagues went on to find similar structures across a range of species, and they have now published the first complete and definitive description of snake clitorises—a finding that could rewrite the narrative of reptilian sex.

The discovery is both surprising and not. The structures are small, fragile, and easy to damage or overlook; Sara Ruane, the assistant curator of herpetology at the Field Museum, in Chicago, says that learning about Folwell’s work was “the first time I have ever even thought about” snake penises having a female analogue. Multiply that sentiment countless times over, and perhaps it explains how researchers mostly missed an entire organ, in an entire group of thousands of animals, until now. But evolutionarily speaking, there’s no reason snakes shouldn’t have clitorises, which arise from the same knot of cells that gives rise to penises. In addition to lizards, snakes’ closest relatives, other groups of reptiles have clitorises, as do mammals.

Snake clitorises made cameos in some previous studies, but Folwell and her colleagues argue that many of them were misidentifications of hemipenes or scent glands. (After I wrote to several of these researchers, two—Oliver Hawlitschek and Stefano Rizzi—got back to me and largely stood by their work, although Hawlitschek noted by email that he would “not exclude that we may have mis-sexed some samples.”) Either way, those types of mistakes might be more avoidable now that researchers have a sharper set of tools with which to determine an individual snake’s sex. Traditionally, when sexing a snake, “you cut a tail open and look for hemipenes,” Ruane told me. “If they’re there, it’s a boy. If they’re not, you assume it’s a female.” But Folwell’s work, Ruane said, convincingly shows that the absence of hemipenes isn’t the only thing that defines a lady snake. Clitorises are very much present.

What’s not totally clear yet is what snake clitorises do. Based on what researchers know about mammalian clitorises, the structures could, when stimulated, make a female snake more receptive to sex by, say, lubricating or relaxing her cloaca. The potential is there: Folwell and her colleagues found that snake clitorises contain a tapestry of blood vessels and nerve endings, hinting that the organs can engorge and feel.

Snake courtship is “quite tactile,” says Jenna Crowe-Riddell, Folwell’s adviser at the University of Adelaide. During their equivalent of foreplay, the reptiles will coil their tails around each other, the male vibrating and undulating; he will sometimes rub his chin up and down the female’s body or flick at her with his tongue. Some of these behaviors could engage the clitorises, making the female more eager to mate or prolonging the coupling event. In certain snake species, a female can store sperm from multiple partners in specialized organs for years, and it’s possible an especially stimulating sexual encounter could lead her to draw from a particular partner’s sperm for multiple clutches of offspring. (How female snakes might actually select sperm, however, isn’t well understood.)

None of that has yet been proved, though, and research in other reptiles hasn’t been much help. One paper from the 1990s suggested that lizard clitorises “were there just to stimulate the male,” Brennan told me. “We were like, Okay, I really doubt that that’s what’s happening.” Whether female snakes get pleasure out of all this is another question. The experts I spoke with were on board with the idea, but it’s challenging to test. Snake faces aren’t the most expressive—although Crowe-Riddell does have some ideas about an experiment involving numbing cream.

In general, scientific research into female genitals is “not always the easiest topic to get funding for,” Folwell told me. Maybe that’s in part driven by the fact that “it’s practically easier to investigate something that is protruding rather than something that is inside,” says Malin Ah-King, an evolutionary biologist and gender researcher at Stockholm University. Cultural biases have raised roadblocks too. Many scientists have historically presumed that females are merely passive receptacles for sperm. Centuries ago, Darwin posited that the evolution of animal sex depends “on a struggle between males for possession of the females”; even some modern scientists have proposed that female fauna, unlike males, might lack the mental capacity to actively choose their mates.

And when pleasure-related organs such as clitorises get involved, there can be downright squeamishness. “We don’t have a problem with male orgasm, because it’s associated with the transmission of sperm,” says Mariella Herberstein, a behavioral ecologist at Macquarie University. But scientists can’t say the same for female pleasure, and the taboo around clitorises has stuck.

Hang-ups such as these keep the scientific focus on males, skewing how humans interpret animal sex lives. Belatedly studying female genitalia “is a recurring pattern” in biology, Ah-King, who has written on the male-centric bias in the study of animal sex, told me. Scientists spent years thinking that male earwigs use their genitals to efficiently dislodge the sperm of other suitors from the female’s body—only to later discover that much of her sperm storage organ is out of his reach. Early work into duck mating suggested that males forcibly propelled their corkscrew-shaped penis deep into females who had little choice in the matter—until the mid-aughts, when Brennan found that duck vaginas can redirect undesirable mates into genital dead-ends.

Snake penises, which come adorned with all sorts of spines, hooks, depressions, flounces, and frills, have been well studied since at least the 1850s, Folwell told me, far predating dedicated inquiries into their female parallels. That might be part of why scientists have long conceived of snake copulation as a male-driven endeavor, with bachelors duking it out for access to females that must then endure sex, Crowe-Riddell told me. Now that the science on clitorises is catching up, she wonders, “Could seduction be a part of it?” Better understanding of snake clitorises could also aid other scientific endeavors. If serpentine clitorises are as diverse as their penises, researchers could have another tool for distinguishing between species, says Leticia Afuang, a herpetologist at the University of the Philippines at Los Baños.

With their lack of fur, warm blood, and limbs, snakes aren’t much like us; their sometimes-venomous bites and muscled, tubular bodies tend to wig people out. But snakes are an essential part of many ecosystems. Their venoms have led to medicines, and their appetite helps with pest control. They even have something to teach us about sex: In the same way that snakes are not just lizards without legs, females are not just males without penises. Perhaps better acquainting ourselves with an oft-maligned body part on an oft-maligned animal could prompt us to reckon with the ways in which we draw boundaries in the natural world—and inspire us to describe life not just by what it lacks, but what it has to offer.